Conventional natural gas delivers up to 25% reductions in greenhouse gases (GHGs) compared to gasoline. Beyond this baseline, NGVs have potential to deliver vastly greater climate change benefits – greenhouse gas emission reductions of 90% or more – through the blending of renewable natural gas (RNG) into the natural gas supply. The widespread adoption of NGVs is needed to catalyze the full development of this fuel by providing a high-value end use market.
This opportunity is already well-underway. According to the RNG Coalition, RNG today accounts for approximately 35% of NGV fuel consumption in California, and 25% nationally. These fractions are expected to grow rapidly in the years ahead as increasingly stringent RFS and LCFS mandates make the economics of RNG even more attractive.
Renewable Natural Gas
Renewable natural gas, also known as biogas, is a renewable, ultra-low carbon fuel that can be produced in a variety of ways, including the capture of landfill gas and the anaerobic digestion of organic feedstocks such as manure or wastewater sludge. Once processed to remove impurities, these RNG sources can be used as a perfect substitute for fossil natural gas, including distribution in the existing natural gas pipeline system and use in NGVs.
Since the capture of RNG removes methane that would otherwise escape into the atmosphere, it can achieve GHG emission reductions of 90% or more on a CO2-equivalent lifecycle basis when used for transportation. And because RNG targets methane, NGVs fueled by RNG are one of the most potent solutions available for reaching California’s goal of cutting methane emissions by 40% by 2030.
Transportation is by far the most attractive end-use market for RNG thanks to the federal Renewable Fuel Standard (RFS) and the California Low Carbon Fuel Standard (LCFS), which require petroleum refiners to purchase credits from low-carbon and renewable vehicle fuel sources. These credit sales have made RNG cost-competitive with fossil natural gas, making NGVs the most powerful driver of the future development of these renewable resources.
A Bridge to Hydrogen
Hydrogen is a zero-emission gaseous fuel that can be produced from a wide range of sources, including natural gas as well as renewable resources. Like RNG, it can be blended into natural gas pipelines and used in NGVs, although unlike RNG it is not a perfect substitute and is limited to blends of 10-20% by volume for technical reasons. There is growing interest in producing hydrogen from solar and wind resources that are too difficult or costly to integrate into the electricity grid and injecting it into the natural gas grid as a method of low-cost, high-volume storage. Such “power to gas” applications are already being used on commercial scale in Germany and will encourage development of renewable resources while simultaneously lowering emissions of natural gas use across all sectors including NGVs.
There are also numerous technical synergies between NGVs and hydrogen fuel cell vehicles (FCVs), which combine zero-emission performance with gasoline-like range and refueling characteristics. The continued development of on-board fuel storage and management systems for natural gas will help accelerate their commercialization for hydrogen, and CNG fueling development similarly serves as a basis for stations dispensing compressed hydrogen.
Natural gas is thus a true “bridge fuel” for hydrogen, and CNG infrastructure developers are well-positioned to play a prominent role in providing FCVs with hydrogen.